A projector is conventionally and generally regarded as a thing to be installed and used within a house or the like. As disclosed in Japanese Patent Laid-open No. 63-118125, Japanese Patent Laid-open No. Hei 4-60538, and the like, a lamp such as a metal halide lamp, a high pressure mercury lamp, a xenon lamp or the like is used as a light source.
However, when a lamp is used as a light source, there are for example problems in that (a) the aperture of a light source unit is increased, resulting in a larger size of the projector as a whole, (b) the light source unit generates a large amount of heat and thus requires a cooling device such as a fan or the like, resulting in an even larger size of the projector as a whole, (c) the fan or the like generates a high level of noise and contributes to an increase in power consumption, (d) light in an undesired and harmful wavelength region such as ultraviolet rays and the like is applied, so that the reliability of a liquid crystal display panel using an organic substance may be impaired, (e) the light source cannot be turned on and off at a high speed, and it is difficult to adjust an amount of light, and (f) frequent lamp replacement is necessary due to the breaking of wire and the life of the lamp.
Therefore, using a light emitting element (illuminant) other than lamps as a light source for a projector is considered.
Specifically, Japanese Patent Laid-open No. 2005-116799 and G. Harbers, M. Keuper, S. Paolini; “Performance of High Power LED Illuminators in Color Sequential Projection Displays”, IDW'03 p 1585 to p 1588 disclose that an LED (Light Emitting Diode) is used as a light source.
Further, Japanese Patent Laid-open (Translation of PCT Application) No. 2005-526288 discloses that a laser is used as a light source, the pumping of the laser is controlled for each pixel in a raster pattern, and laser light emitted from the laser is scanned on the raster pattern by a scanner formed of two scanning mirrors to display a two-dimensional image on the raster pattern.
As regards the laser, semiconductor lasers, so-called LDs, and solid-state lasers such as a solid-state laser pumped by a semiconductor laser (DPSSL: Diode Pumped Solid State Laser) and the like have been realized. As for the size thereof, the length of one side of a semiconductor laser can be made to be a few hundred μm, and the length of one side of a nonlinear optical crystal of a solid-state laser in a 100-mW output class can be made to be a few mm.
In addition, as compared with the metal halide lamp or the like, the semiconductor laser or the solid-state laser has a long life, hardly needs replacing, has a high light emission efficiency, generates a small amount of heat, and is easy to cool.
In addition, depending on the type and composition of a crystal, the semiconductor laser or the solid-state laser can be made to emit light of an optimum wavelength for display in each of wavelength regions of red, green, and blue, so that color purity is improved, and light unnecessary for display such as infrared light, ultraviolet light and the like is not emitted.
Further, the semiconductor laser or the solid-state laser can be switched on and off instantaneously, so that an amount of emitted light can be controlled easily.